Magnetic tape cartridge

ABSTRACT

Disclosed herein is a magnetic tape cartridge including a cartridge case. In the cartridge case, a single reel with magnetic tape wound thereon is rotatably housed, and a leader pin coupled with a leading end of the magnetic tape is caught by a pin catching member of a recording-reproducing unit and is inserted into a tape leader opening formed in the cartridge case. The magnetic tape cartridge also includes a pin retaining spring member which elastically engages the leader pin so that the leader pin is detachably retained at a predetermined position within the cartridge case. Furthermore, a wall surface is provided in the cartridge case so that when the leader pin is inserted into the cartridge case, displacement of the pin retaining member due to the engagement of the pin retaining member with the leader pin is regulated within a predetermined range.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a magnetic tape cartridge, inwhich a single tape reel with magnetic tape wound thereon is rotatablyhoused within a cartridge case and a tape leader pin is coupled with theleading end portion of the magnetic tape.

[0003] 2. Description of the Related Art

[0004] In the magnetic tape cartridges, which are used as storage mediumto be employed in external storage units for computers, etc., there isknown a type where a single tape reel with magnetic tape wound thereonis rotatably housed within a cartridge case. This magnetic tape isemployed as a data archiving tape for computers, etc., and storesimportant information. For this reason, the magnetic tape cartridge isconstructed so that trouble, such as tape jamming, etc., does not occurand that the magnetic tape is not pulled out from the cartridge caseunexpectedly.

[0005] Also, a tape leader pin is coupled to the leading end of themagnetic tape. When this magnetic tape cartridge is loaded into arecording-reproducing unit, a pin catching member on the side of therecording-reproducing unit engages the tape leader pin and pulls out themagnetic tape from the cartridge case. On the other hand, when themagnetic tape cartridge is unloaded from the recording-reproducing unit,the magnetic tape is wound on the reel and the tape leader pin isreturned into the cartridge case by the pin catching member. The tapeleader pin is detachably retained in a predetermined position, by a pinretaining spring member provided within said cartridge case so that itfaces the tape leader opening of the cartridge case.

[0006] The aforementioned tape leader pin is illustrated in FIG. 1A.This tape leader pin P and magnetic tape T are coupled with each other,as illustrated in FIG. 1B. The tape leader pin P is constructed of a pinmain body 5 and a clamp member 6, as disclosed in Japanese UnexaminedPatent Publication No. 11(1999)-232826. The pin main body 5 is formed,for example, from stainless steel and consists of a tape clamp portion 5a interposed between a pair of inner flange portions 5 b, small-diameterportions 5 c formed outside the inner flange portions 5 b, and outerflange portions 5 d formed outside the small-diameter portions 5 c. Theclamp member 6 is formed, for example, from synthetic resin. This clampmember 6 is equipped with an axial slit 6 a and has a C-shaped crosssection. The clamp member 6 is inserted elastically on the tape clampportion 5 a of the pin main body 5, and magnetic tape T is clampedbetween the clamp member 6 and the tape clamp portion 5 a.

[0007]FIG. 2 illustrates a conventional magnetic tape cartridgedisclosed in Japanese Unexamined Patent Publication No. 2000-36179. Notethat in FIG. 2, the right side in the figure is the front side of thecartridge case, because the cartridge case is inserted toward the rightside when it is loaded into a recording-reproducing unit.

[0008] In this magnetic tape cartridge, a single tape reel (not shown)with magnetic tape T coupled at its leading end with a tape leader pin Pis rotatably housed within a cartridge case 4 consisting of an uppercase (not shown) and a lower case 3 fastened together by means of smallbolts, etc. A tape leader opening 10 for leading the magnetic tape T isformed in one side wall of the cartridge case 4. This tape leaderopening 10 is constructed so that it is opened and closed by a slidedoor (not shown) urged in a closing direction with a spring member (notshown).

[0009] The tape leader pin P, coupled with the leading end of themagnetic tape T, and having construction such as that shown in FIG. 1,is inserted in and out of the magnetic cartridge through the tape leaderopening 10. The top and bottom walls inside the tape leader opening 10are provided with pin housing recesses 45 into which the upper and lowerflange portions 5 d of the leader pin main body 5 are inserted. Also,there is formed an insertion guide portion 21 extending linearly fromthe pin housing recess 45 toward the tape leader opening 10.

[0010] A pin retaining member 50, for detachably retaining the tapeleader pin P in the pin housing recess 45, is formed from a plate springmember having a hairpin-shaped cross section. The pin retaining member50 has an attaching plate portion 50 a which extends vertically betweenthe upper and lower cases. The attaching plate portion 50 a is clampedbetween (1) bosses 41 provided on the bottom surface of the top wall ofthe upper case and the top surface of the bottom wall of the lower case3 along the inside surface of the case side wall 3 b, and (2) the sidewall 3 b. The pin retaining member 50 further has a pair of upper andlower elastic arm portions 50 b which extend from the upper and lowerends of the proximal portion 50 d of the attaching portion 50 a towardthe tape leader opening 10. The outer end portions of the upper andlower elastic arm portions 50 b are formed into pin retaining portions50 c, which abut the outer peripheral surfaces of the upper and lowerflange portions 5 d of the leader pin main body 5.

[0011] On the other hand, the pin housing recess 45 of the cartridgecase 4 has an abutting surface in the form of a circular arc whichreceives the outer peripheral surface of the flange portion 5 d of theleader pin main body 5. However, the right side portion, on the side ofthe pin retaining member 50, of the abutting surface has been removed inorder to assure installation space for the elastic arm portions 50 b andpin retaining portions 50 c of the pin retaining member 50.

[0012] The tape leader pin P retained in the pin housing recess 45 ispulled out of the cartridge case 4 by a pin catching member 80, called aleader block, which is provided on the side of a recording-reproducingunit. The pin catching member 80 has an engagement cutout 80 a whichengage with the upper and lower small-diameter portions 5 c (see FIG. 1)of the leader pin main body 5. When the engaging operation is performed,the pin catching member 80 first moves linearly in the direction ofarrow A toward the tape leader opening 10 and enters the tape leaderopening 10 through a side opposite to the case side wall 3 b withrespect to the tape leader pin P. Then, the outer end of the pincatching member 80 rotates in the direction of arrow B toward the tapeleader pin P. The engagement cutout 80 a of the pin catching member 80is caught on the small-diameter portion 5 c of the tape leader pin P andis moved back in the direction of arrow C. As a result, the tape leaderpin P is pulled out of the cartridge case 4 through the tape leaderopening 10. In this manner, the mechanism of the recording-reproducingunit is simplified.

[0013] On the other hand, when the magnetic tape cartridge is taken outfrom the recording-reproducing unit, the pin catching member 80 holdingthe tape leader pin P advances linearly toward the tape leader opening10 in the direction opposite to the direction of arrow C. After the tapeleader pin P has been retained in the pin housing recess 45, the pincatching member 80 is returned via the tape leader opening 10 along thereverse route of the aforementioned route.

[0014] In the tape leader pin P of FIG. 1, incidentally, there is apossibility that the tape leader pin P will be disengaged from themagnetic tape T because of insufficient clamping force, since thecoefficient of friction between the magnetic tape T and the pin mainbody 5 (or the clamp member 6) is low. More specifically, in order toreduce the sliding friction between the magnetic tape T and the magnetichead, a lubricating agent is often coated on the magnetic layer or topsurface of the magnetic tape T so that the coefficient of friction isreduced. Similarly, a lubricating agent is coated on the bottom surfaceof the magnetic tape T. In that case, the coefficient of frictionbetween the pin main body 5 (or the clamp member 6) formed fromstainless steel and the magnetic tape T varies with the type of themagnetic tape T. When this coefficient of friction is small, there arecases where the clamping force by the insertion of the clamp member 6onto the tape leader pin P is reduced.

[0015] In addition, when the tape leader pin P is held and pulled out ofthe tape leader opening 10 of the cartridge case 4 by the pin catchingmember 80, as described above, the pin catching member 80 is insertedinto the tape leader opening 10 in the direction of arrow A and is thenrotated in the direction of arrow B to catch the tape leader pin P. Forthis reason, there is a problem that engagement between the pin catchingmember 80 and the tape leader pin P cannot be reliably performed,because the tape leader pin P is pushed and moved by the pin catchingmember 80 when the pin catching member 80 rotates in the direction ofarrow B and engages the tape leader pin P.

[0016] That is, when the pin catching member 80 rotates in the directionof arrow B and engages the tape leader pin P, there are cases whereforce is exerted on the tape leader pin P in the direction of arrow B bythe pin catching member 80. In such a case, since the right side portionof the abutting surface of the housing recess 45 has been removed, thespring force of the pin retaining member 50 cannot resist the rightwardforce exerted on the tape leader pin P and therefore the tape leader pinP will be moved out of the pin housing recess 45 or will tilt. As aresult, there is a fear that the pin catching member 80 cannot engagethe tape leader pin P correctly and the loading operation will not beperformed with reliability.

[0017] Hence, it has been proposed to provide an abutting portion on aside near the pin retaining member to receive the flange portion 5 d ofthe tape leader pin P and regulate movement of the tape leader pin Pduring engagement. However, in that case, space for installing the pinretaining member is narrowed, so it becomes difficult to install thehairpin-shaped pin retaining member 50 equipped with the long elasticarm portion 50 b.

[0018] To solve this problem, a pin retaining member with a relativelyshort elastic arm portion can be employed. In that case, if theretaining portion of the outer end of the elastic arm portion of the pinretaining member is forcibly pushed by the tape leader pin P when thetape leader pin P is inserted into the pin housing recess 45 during theunloading operation, there is another problem that plastic deformationwill occur near the boundary portion between the attaching portion andshort elastic arm portion of the pin retaining member and therefore theshort elastic arm portion will no longer return to the originalposition.

[0019] Furthermore, as described in the aforementioned JapaneseUnexamined Patent Publication No. 11(1999)-232826, there is a magnetictape cartridge having separate pin retaining members. The pin retainingmembers are respectively equipped with elastic arm portions and areindependently installed in the upper and lower cases. However, theelastic arm portions of the pin retaining members are equipped at theirouter ends with angled pin-retaining portions for retaining the flangeportions 5 d of the pin leader pin P, and the upper and lower elasticarm portions and pin retaining portions are approximately the same inshape. Because of this, the upper and lower pin retaining members areapproximately the same in spring characteristic.

[0020] Therefore, when the tape leader pin P is returned into thecartridge case by a pin catching member provided on a drive unit, theupper and lower flange portions 5 d of the tape leader pin P are broughtinto contact with the pin retaining portions of the pin retainingmembers at approximately the same time and are subjected toapproximately the same elastic force. Because of this, the tape leaderpin P will be caught on the pin retaining portions and therefore smoothengagement between the tap leader pin P and the pin retaining memberswill be disturbed.

SUMMARY OF THE INVENTION

[0021] The present invention has been made in view of the aforementionedcircumstances. Accordingly, it is a first important object of thepresent invention is to provide a magnetic tape cartridge that iscapable of enhancing a force of clamping the leading end portion ofmagnetic tape to a tape leader pin to assure reliability.

[0022] A second important object of the invention is to provide amagnetic tape cartridge which is capable of preventing plasticdeformation of a pin retaining member during an unloading operation,while assuring a reliable loading operation by preventing movement of atape leader pin when a pin catching member engages the tape leader pinduring a loading operation

[0023] A third important object of the invention is to provide amagnetic tape cartridge which is capable of performing smooth engagementbetween a tape leader pin and a pin retaining member by preventing a pincatching member from being caught on the pin retaining member when thetape leader pin is returned into a cartridge case.

[0024] To achieve the aforementioned objects and in accordance with thepresent invention, there is provided a first magnetic tape cartridgecomprising: a cartridge case; a single reel rotatably housed in thecartridge case, the reel having magnetic tape wound thereon; and aleader pin, coupled with a leading end of the magnetic tape, for leadingthe magnetic tape;

[0025] wherein the leader pin has both a pin main body equipped with atape clamp portion on which the leading end of the magnetic tape iswound, and a clamp member for fixing the magnetic tape to the tape clampportion; and

[0026] at least either a surface of the tape clamp portion or an insidesurface of said tape clamp member is roughened with an average surfaceroughness Rz of 7 μm or less.

[0027] According the first magnetic tape cartridge of the presentinvention, at least either the surface of the tape clamp portion or theinside surface of said tape clamp member is roughened with an averagesurface roughness Rz of 7 μm or less. Therefore, even if the surface ofmagnetic tape has a low coefficient of friction, the roughened surfacewill enhance the frictional resistance between itself and the magnetictape and will increase the clamping force between itself and themagnetic tape. Thus, disengagement of the tape leader pin from themagnetic tape can be prevented and reliability can be assured.

[0028] In accordance with the present invention, there is provided asecond magnetic tape cartridge comprising:

[0029] a cartridge case in which a single reel with magnetic tape woundthereon is rotatably housed and a leader pin coupled with a leading endof the magnetic tape is caught by a pin catching member of arecording-reproducing unit and is inserted into a tape leader openingformed in the cartridge case; and

[0030] a pin retaining spring member which elastically engages theleader pin so that the leader pin is detachably retained at apredetermined position within the cartridge case;

[0031] wherein a wall surface is provided in the cartridge case so thatwhen the leader pin is inserted into the cartridge case, displacement ofthe pin retaining member due to the engagement of the pin retainingmember with the leader pin is regulated within a predetermined range.

[0032] In the second magnetic tape cartridge, the aforementioned pinretaining member has an elastic arm portion, and the aforementioned wallsurface faces the elastic arm member with a predetermined space and isapproximately perpendicular to a direction in which the elastic armportion is displaced. The predetermined space is set within an elasticlimit of the elastic arm portion. Furthermore, the aforementioned wallsurface may have a configuration which corresponds to a pin retainingportion formed in an outer end of the elastic arm portion, and may havea protruding portion which faces the pin retaining portion with apredetermined space.

[0033] According the second magnetic tape cartridge of the presentinvention, the wall surface is provided in the cartridge case so thatwhen the leader pin is inserted into the cartridge case, displacement ofthe pin retaining member due to the engagement of the pin retainingmember with the leader pin is regulated within a predetermined range.Therefore, in the case of employing a pin retaining member equipped witha short elastic arm portion which does not require a large installationspace, plastic deformation of the elastic arm portion can be prevented.

[0034] Therefore, an abutting portion, for receiving the flange portionof the tape leader pin and regulating movement of the tape leader pinduring engagement, can be formed in the pin housing recess near the pinretaining member. Thus, even if the tape leader pin is pushed toward thefront surface of the cartridge case when the pin catching member engagesthe tape leader pin during the loading operation, movement of the tapeleader pin toward the case front surface can be prevented by theabutting surface formed near the pin retaining member and therefore thetape leader pin can be prevented from being moved out of the pin housingrecess or tilting. Since the tape leader pin can be correctly held bythe pin catching member, a reliable loading operation can be performedand operational reliability can be assured.

[0035] In accordance with the present invention, there is provided athird magnetic tape cartridge comprising:

[0036] a cartridge case having upper and lower cases fastened together;

[0037] a single reel, rotatably housed within the cartridge case, whichhas magnetic tape wound thereon;

[0038] a leader pin, coupled with a leading end of the magnetic tape,which has upper and lower flange portions at both ends;

[0039] upper and lower pin retaining spring members which elasticallyengage the upper and lower flange portions of the leader pin so thatwith an axis of the leader pin directed in a vertical direction, theleader pin is detachably retained between the upper and lower cases;

[0040] the leader pin being constructed so that it is caught by a pincatching member of a recording-reproducing unit and moved out of thecartridge case and that it is returned into the cartridge case by thepin catching member;

[0041] wherein the upper and lower pin retaining members have differentspring characteristics so that when the leader pin is returned into thecartridge case, one of the pin retaining members starts engaging withthe flange portion of the leader pin earlier than the other.

[0042] In the third magnetic tape cartridge of the present invention,the upper and lower pin retaining members may have upper and lowerelastic arm portions which differ in at least one of wall thickness,shape, or material so that the different spring characteristics areobtained. Furthermore, the upper and lower pin retaining members mayhave upper and lower elastic arm portions which are equipped with upperand lower pin retaining portions bent at difference angles so that thedifferent spring characteristics are obtained.

[0043] According the third magnetic tape cartridge of the presentinvention, the upper and lower pin retaining members have differentspring characteristics so that when the leader pin is returned into thecartridge case, one of the pin retaining members starts engaging withthe flange portion of the leader pin earlier than the other. This canprevent the pin catching member from being caught on the pin retainingmember and make possible smooth engagement between the pin leader pinand the pin retaining member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be described in further detail withreference to the accompanying drawings wherein:

[0045]FIG. 1A is an exploded perspective view showing a tape leader pinwhich is equipped in a magnetic tape cartridge;

[0046]FIG. 1B is a sectional view showing the state in which the tapeleader pin is coupled with magnetic tape;

[0047]FIG. 2 is a plan view showing a conventional magnetic tapecartridge, the upper case having removed to show a loading operation;

[0048]FIG. 3 is an exploded perspective view showing a magnetic tapecartridge constructed according a first embodiment of the presentinvention;

[0049]FIG. 4 is a perspective view showing the tape leader pin of themagnetic tape cartridge of FIG. 3 and the magnetic tape to be coupledwith the tape leader pin;

[0050]FIG. 5 is a sectional view showing the state in which the tapeleader pin and magnetic tape of FIG. 4 are coupled with each other;

[0051]FIG. 6 is a sectional view showing the state in which a variationof the tape leader pin of FIG. 4 are coupled with the magnetic tape;

[0052]FIG. 7 is a perspective view showing a pin retaining memberprovided in the magnetic tape cartridge of FIG. 3;

[0053]FIG. 8 is a front view showing the state in which a slide door inthe magnetic tape cartridge of FIG. 3 has been opened to show a tapeleader opening;

[0054]FIG. 9 is a plan view showing the tape leader opening, the uppercase having been removed;

[0055]FIG. 10 is an enlarged perspective view showing the pin housingrecess of FIG. 9;

[0056]FIG. 11 is a sectional view showing the case where a wall facingthe elastic arm portion of the pin retaining member of FIG. 9 isvertical;

[0057]FIG. 12 is a diagram used for explaining how the elastic armportion is displaced when a wall facing the elastic arm portion is aninclined surface;

[0058]FIG. 13 is a plan view showing a variation of the pin retainingmember shown in FIG. 7;

[0059]FIG. 14 is a plan view showing a magnetic tape cartridgeconstructed according a second embodiment of the present invention, theupper case having been removed;

[0060]FIG. 15 is a sectional view taken substantially along ling XV-XVof FIG. 14;

[0061]FIG. 16 is a sectional view of the magnetic tape cartridge in FIG.14 taken substantially along ling XVI-XVI of FIG. 14;

[0062]FIG. 17 is a perspective view of the pin retaining member of FIG.14;

[0063]FIG. 18 is a side view showing a variation of the pin retainingmember;

[0064]FIGS. 19A and 19B are plan views showing another variation of thepin retaining member; and

[0065]FIGS. 20A and 20B are plan views showing still another variationof the pin retaining member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] Referring now in greater detail to the drawings and initially toFIG. 3, there is shown a magnetic tape cartridge 1 in accordance with afirst embodiment of the present invention. The magnetic tape cartridge 1has a cartridge case 4, formed by fastening an upper case 2 and a lowercase 3 together with small volts. A single tape reel 7 with magnetictape T coupled at its leading end with a tape leader pin P is rotatablyhoused within the cartridge case 4. A tape leader opening 10 for leadingthe magnetic tape T is formed in one side wall 2 b of the upper case 2and one side wall 3 b of the upper case 3. This tape leader opening 10is opened and closed by a slide door 11 urged in a closing direction bymeans of a spring (not shown). A door rail 12 in the form of a groove(see FIGS. 9 and 10) along which the slide door 11 slides is formed nearthe tape leader opening 10.

[0067] The upper and lower cases 2 and 3 are approximately rectangularin shape, and upper and lower side walls 2 a and 3 a are provided on thecircumferences of the top and bottom walls 2 b and 3 b. The upper andlower cases 2 and 3 further have arcuate inside walls 3 c (shown onlyfor the lower case 2) extending along the outer periphery of the tapereel 7. The upper and lower cases 2 and 3 are fastened together by smallbolts, with the four boss portions 3 d (only three are shown) of thelower case 3 in contact with the boss portions (not shown) of the uppercase 2.

[0068] A center hole 3 e is formed in the central portion of the lowercase 3 to rotate the tape reel 7 by the drive shaft of a drive unit (notshown). A write inhibit member 13 is disposed on the rear end portion sothat it is slidable. The tape reel 7 is provided at the central portionthereof with a rotation regulating mechanism 15 for restrict rotation ofthe tape reel 7 when it is not used.

[0069] Although not shown, a reel plate is attached on the bottomsurface of the tape reel 7 to retain a magnet type rotation drive meanson the central portion of the tape reel 7. The outer peripheral portionof the tape reel 7 is provided with a reel gear which meshes with thedrive gear of the rotation drive means. When the reel gear and the drivegear are in a meshed state, the rotation regulating means 15 is releasedso that the paper reel 7 is free to rotate.

[0070] In the magnetic tape cartridge 1, the tape leader pin P isretained in a pin housing recess 20 formed near the tape leader opening10, with the magnetic tape T completely wound on the tape reel 7 whennot being used. This housing recess 20 is continuous to an insertionguide portion 21 (see FIG. 10). The insertion guide portion 21 isconstructed so that the end portion of the tape leader pin P can beguided to the pin housing recess 20. Also, there is disposed a pinretaining member 9 consisting of a plate spring member. The pinretaining member 9 is used for detachably retaining the tape leader pinP in the pin housing recess 20.

[0071] The tape leader pin P consists of a pin main body 5 and a clampmember 6, as illustrated in FIG. 4. The pin main body 5 has a tape clampportion 5 a in the form of a shaft at its central portion. The tape clamportion 5 a is used to clamp the end portion of the magnetic tape Tbetween it and the clamp member 6. The pin main body 5 also has flangeportions 5 b in the form of a thin plate at the upper and lower ends ofthe tape clamp portion 5 a. In addition, small-diameter portions 5 c,which are engaged and retained by the pin catching member of arecording-reproducing unit, are formed outside the flange portions 5 b.Furthermore, relatively thick flange portions 5 d for engaging with thecartridge case 4 are formed at the opposite ends of the pin main body 5.The pin main body 5 is formed, for example, from bar stainless steel bycutting, and the length of the tap clamp portion 5 a corresponds to thewidth of the magnetic tape T.

[0072] The surface of the tape clamp portion 5 a of the pin main body 5is roughened with an average surface roughness Rz of 7 μm or less. Theroughening increases the frictional resistance between the surface ofthe tape clamp portion 5 a and the magnetic tape T, so the force ofclamping the magnetic tape T enhances. The roughening of the tape clampportion 5 a is performed by knurling, etc.

[0073] The clamp member 6 is a resin molded product and has an axiallength which corresponds to the length of the tape clam portion 5 a ofthe pin main body 5. This clamp member 6 is provided with an axial slit6 a extending over the overall length thereof and has a C-shaped crosssection. The width of the slit 6 a is narrower than the outside diameterof the tape clamp portion 5 a. Therefore, if the clamp member 6 isinserted elastically on the outer periphery of the tape clamp portion 5a while being deformed so that the slit 6 a is outstretched, the innerperipheral surface 6 a of the clamp member 6 is pressed against theouter periphery of the tape clamp portion 5 a, and the magnetic tape Tis clamped between the inner peripheral surface 6 a of the clamp member6 and the outer periphery of the tape clamp portion 5 a.

[0074] The inner peripheral surface 6 a of the clamp member 6 isroughened with an average surface roughness Rz of 7 μm or less. Theroughening increases the frictional resistance between the innerperipheral surface 6 b and the magnetic tape T, so the clamping forceenhances. The roughening of the inner peripheral surface 6 b isperformed by a sand blasting process for a molding die, etc.

[0075] As shown in FIG. 4, reinforcement tape RT may be stuck on theoutside surface or inside surface of the leading end portion of themagnetic tape T which is coupled with the pin main body 5. For example,in the clamped state shown in FIG. 5, the top surface of thereinforcement tape RT contacts the surface of the tape clamp portion 5a, while the outside surface of the magnetic tape T contacts the innerperipheral surface 6 b of the clamp member 6. In this case, at least theinner peripheral surface 6 b of the clamp member 6 which contacts themagnetic tape T is roughened as described above. On the other hand, inthe case where the reinforcement tape RT is stuck on the outside surfaceof the magnetic tape T, the tape clamp portion 5 a of the pin main body5 is roughened as described above. Furthermore, both the surface of thetape clamp portion 5 a and the inner peripheral surface 6 a of the clampmember 6 may be roughened.

[0076] According to the first embodiment, at least either the surface ofthe tape clamp portion 5 a or the inner peripheral surface 6 a of theclamp member 6 is roughened. Therefore, in the case where the pin mainbody 5 is coupled to the leading end portion of the magnetic tape T byinserting the clamp member 6 on the pin main body 5, the coefficient offriction between the pin main body 5 (and/or the clamp member 6) and themagnetic tape T becomes high and the magnetic tape T is clamped withincreased frictional force. Thus, the magnetic tape cartridge can beprevented from becoming unusable due to disengagement of the tape leaderpin P from the magnetic tape T.

[0077]FIG. 6 illustrates a clamp member 6′ differing from that shown inFIGS. 4 and 5.

[0078] The clamp member 6′ is made of steel and has a C-shaped crosssection. This clamp member 6′ has an axial length that corresponds tothe length of the tape clam portion 5 a of the pin main body 5. Theclamp member 6′ is provided with an axial slit 6 a′ extending over theoverall length thereof. The width of the slit 6 a′ is greater than theoutside diameter of the tape clamp portion 5 a. The clamp member 6′ isinserted on the outer periphery of the tape clamp portion 5 a throughthe slit 6 a′. Then, the slit 6 a′ is caulked to clamp the magnetic tapeT between the clamp member 6′ and the tape clamp portion 5 a. Also,elastomer E is interposed between the inner peripheral surface 6 b′ theclamp member 6′ and the magnetic tape T wound on the outer periphery ofthe tape clamp portion 5 a.

[0079] The elastomer E is used for preventing the magnetic tape T frombeing damaged when the clamp member 6′ is caulked. A natural orsynthetic polymer having elastic properties, such as natural rubber andsynthetic rubber, is used. The elastomer E is coated beforehand on theinner peripheral surface 6 b′ of the clamp member 6′.

[0080] As with the aforementioned case, the surface of the tape clampportion 5 a of the pin main body 5 is roughened with an average surfaceroughness Rz of 7 μm or less. The roughening increases the frictionalresistance between the tape clamp portion 5 a and the magnetic tape T,so the force of clamping the magnetic tape T enhances.

[0081] The surface of the tape clamp portion 5 a of the pin main body 5,or the inner peripheral surface 6 a′ of the clamp member 6′, isroughened with an average surface roughness Rz of 7 μm or less byvarious roughening methods. On the other hand, if the surface isroughened to greater than the upper limit, particularly in the casewhere the surface of the tape clamp portion 5 a or the surface of themolding die for the clamp member 6 is roughened by a sand blastingprocess, the very small protrusions on the roughened surface will bedamaged and therefore the problem of dust will arise. Therefore, it ispreferable that the average surface roughness Rz be 7 μm or less andfurther preferable that it be about 3 μm or less.

[0082] As shown in FIG. 7, the pin retaining member 9 has an attachingportion 9 a in the form of a rectangular plate. With the upper case 2and the lower case 3 fastened together, the retaining portion 9 a isengaged and held by a spring holding portion 23 provided near the caseside walls (front walls) 2 b and 3 b, as shown in FIG. 9 (although theupper case 2 is not shown, it is symmetrical with the lower case). Thepin retaining member 9 also has a pair of elastic arm portions 9 bextending obliquely from the upper and lower end portions of theattaching portion 9 a toward the tape leader pin P. The elastic armportions 9 b have pin retaining portions 9 c at their outer ends,respectively. The pin retaining portions 9 c elastically abut the outerperipheries of the upper and lower flange portions 5 d of the pin mainbody 5 of the tape leader pin P.

[0083] The pin retaining portions 9 c are bent so that they projecttoward the tape leader pin P. If the tape leader pin P inserted into thetape leader opening 10 is brought into contact with the outer inclinedsurfaces of the pin retaining portions 9 c, the elastic arm portions 9 bare elastically deformed and the tape leader pin P is retained withinthe pin housing recess 20 by the inner inclined surfaces of the pinretaining portions 9 c. In addition, engaging recesses 9 d are providedin the top and bottom edges of the attaching portion 9 a.

[0084] The spring holding portion 23 for holding the pin retainingmember 9 is equipped with ribs 23 a formed on the inside surfaces of theside walls (front walls) 2 b and 3 b of the upper and lower cases 2 and3, and a protrusion 23 b formed between the ribs 23 a and on the bottomsurface. If the attaching portion 9 a of the pin retaining member 9 isinserted between the ribs 23 a and the protrusion 23 b, the engagingrecess 9 d is fitted on a protruding portion 23 c on the bottom surface.In this manner, the pin retaining member 9 is held by the spring holdingportion 23. Furthermore, the spring holding portion 23 is provided witha tilt regulating portion 23 d for holding the proximal portion of theattaching portion 9 a of the pin retaining member 9 remote from theelastic arm portion 9 b in an upright state.

[0085] The pin housing recess 20 is formed into a U shape by aperipheral surface 20 a and a flat bottom surface 20 b. The peripheralsurface 20 a is formed by a semicircular surface and parallel surfacesextending from the opposite ends of the semicircular surface. The heightor depth of the peripheral surface 20 a is lower than that of the flangeportion 5 d of the tape leader pin P, as illustrated in FIG. 8. Thearcuate surface of the peripheral surface 20 a has a bore diameter whichcorresponds to the outside diameter of the flange portion 5 d of thetape leader pin P so that the tape leader pin P housed is held in thecenter position thereof. The peripheral surface 20 a further has asupport portion 22 which abuts the flange portion 5 d of the tape leaderpin P to regulate movement of the tape leader pin P when the tape leaderpin P is pushed in a right direction in FIG. 9 by the rotationalmovement of the pin catching member 80 (see FIG. 2) of arecording-reproducing unit in the direction of arrow B that is performedduring the loading operation.

[0086] The insertion guide portion 21, disposed closer to the tapeleader opening 10 than to the pin housing recess 20, has a flat surface21 a, continuous to the bottom surface 20 b of the housing recess 20,and an inclined surface 21 b. The insertion guide portion 21 further hasside surfaces 21 c at the opposite sides. The side surfaces 21 c widenin width toward the tape leader opening 10 and are connected to theperipheral surface 20 a of the pin housing recess 20. A door rail 12 isformed in the side surfaces 21 c near the tape leader opening 10. Anoblique recess 25 is formed in the inclined surface 21 c on the casefront side (right side of FIG. 10) to install the pin retaining member 9and is provided so that the pin retaining-portion 9 c of the elastic armportion 9 b can abut the flange portion 5 d of the tape leader pin P.

[0087] As shown in FIG. 11, a wall surface of the oblique recess 25remote from the pin housing recess 20 extends approximately verticallyfrom the bottom surface of the recess 25 and forms a vertical wallsurface 30 which faces the elastic arm portion 9 b of the pin retainingmember 9 through a space W. Even if the elastic arm portion 9 b isforcibly pushed when the tape leader pin P is inserted into the tapeleader opening 10, the elastic arm portion 9 b will abut the verticalwall surface 30 and therefore further displacement of the elastic armportion 9 b will be prevented. The space W is set within the elasticlimit of the elastic arm portions 9 b so that the upper and lower armportions 9 b are prevented from being plastically deformed at theboundary portion between the attaching portion 9 a and the upper armportion 9 b and the boundary portion between the attaching portion 9 aand the lower arm portion 9 b.

[0088] In the case where the wall surface facing the elastic arm portion9 b is not the vertical wall surface 30 but an inclined wall surface 31such as that shown in FIG. 12, incidentally, the elastic arm member 9 bwill be moved upward along the inclined wall surface 31 by the pushingforce exerted on the tape leader pin P and will exceed its elasticlimit. Consequently, there is a possibility that the elastic arm portion9 b will no longer return to the original position.

[0089] In addition, instead of the vertical wall surface 30, aprotruding portion 32 may be provided so that it faces a pin retainingportion 9 c formed in the outer end of the elastic arm portion 9 b ofthe pin retaining member 9, as shown in FIG. 13, for example. Theprotruding portion 32 has a configuration which corresponds to the pinretaining portion 9 c curved convexly toward the tape leader pin P, andextends toward the pin retaining portion 9 c.

[0090] According to the first embodiment, as described above, thevertical wall surface 30 or protruding portion 32 is provided in thecartridge case 4 so that when the magnetic tape cartridge 1 is unloaded,the displacement of the elastic arm portion 9 b by the tape leader pin Pcan be regulated within a predetermined range. Thus, even in the case ofemploying the pin retaining member 9 equipped with short elastic armportions 9 b which do not require a large installation space, plasticdeformation of the elastic arm portion 9 b can be prevented. Therefore,the abutting portion 22 for receiving the tape leader pin P to regulatemovement of the tape leader pin P during engagement can be formed on aside, near the pin retaining member 9, of the pin housing recess 20.This prevents the tape leader pin P from being moved out of the housingrecess 20 or tilting when the pin catching member rotates and engageswith the tape leader pin during the loading operation. Thus, the loadingoperation can be performed with reliability.

[0091] FIGS. 14 to 17 illustrate a magnetic tape cartridge constructedaccording to a second embodiment of the present invention.

[0092] A tape leader pin P in the second embodiment has the sameconstruction as that shown in FIG. 4. The upper and lower flangeportions 5 d of the tape leader pin P are inserted into recesses 45,formed in the bottom surface of the top wall of an upper case 2 and thetop surface of the bottom wall of a lower case 3. Also, the upper andlower flange portions 5 d are detachably retained by a pin retainingmember 60, clamped between the upper and lower cases 2 and 3, whichconsists of a plate spring member.

[0093] As illustrated in FIG. 17, the pin retaining member 60 isconstructed integrally by an attaching portion 60 a in the form of aflat plate, a connecting portion 60 d in the form of a semi cylinderconnected to one end of the attaching portion 60 a, a pair of parallelelastic arm portions 60 b extending horizontally from the upper andlower end portions of the connecting portion 60 d, and pin retainingportions 60 c formed in the outer ends of the arm portions 30 b. The pinretaining member 60 has a hairpin-shaped cross section, as shown in FIG.14. The upper and lower pin retaining portions 60 c and 60 c are bent atpredetermined angles, respectively. If the outer peripheries of theflange portions 5 d of the tape leader pin P are brought into contactwith the outer inclined surfaces of the bent portions of the upper andlower pin retaining portions 60 c and 60 c, the arm portions 60 b and 60b are deflected and the flange portions 5 d are retained within therecesses 45 by the inner inclined surface of the bent portions. However,the bent portions of the upper and lower pin retaining portions 60 cdiffer in angle. For example, in the embodiment shown in FIG. 17, thelower pin retaining portion 60 c is bent more acutely than the upper pinretaining portion 60 c. As a result, when the tape leader pin P isreturned into the cartridge case 1, the upper pin retaining portion 60 cstarts engaging with the flange portion 5 d earlier than the lower pinretaining portion 60 c.

[0094] The upper edges of the connecting portion 60 d and attachingportion 60 a of the pin retaining member 60 are on the same plane as theupper edge of the upper arm portion 60 b, and the lower edges of theconnecting portion 60 d and the attaching portion 60 a are on the sameplane as the lower edge of the lower arm portion 60 b. The upper andlower edges of the attaching portion 60 a and connecting portion 60 d ofthe pin retaining member 60 constitute a portion for fixing the pinretaining member 60 to the cartridge case 4.

[0095] On the other hand, in a portion for attaching the pin retainingmember 60, which is provided in the upper and lower cases 2 and 3 of thecartridge case 4, two cylindrical bosses 41 are projected from the topsurface of the bottom wall 3 a of the lower case 3 along the inside wallsurface of the side wall 3 b of the lower case 3 with a predeterminedspace, as shown in FIGS. 14 and 15 which show the attaching portion forthe pin retaining member 60, provided in the lower case 3. In addition,between the bosses 41 and the inside wall surface of the side wall 3 bof the lower case 3, there is provided a first narrow gap into which thelower end portions of the attaching portion 60 a and connecting portion60 d of the pin retaining member 60 are fitted. Furthermore, between aprotruding portion 48 and the inner boss 41, there is provided a secondnarrow gap 47 (see FIG. 15) into which the lower end portion of theconnecting portion 60 d is fitted. With this arrangement, the pinretaining member 60 is attached on the lower case 3, with the lower endportions of the attaching portion 60 a and the connecting portion 63 dfitted into the aforementioned first gap and second gap 47, as shown inFIG. 14.

[0096] As shown in FIGS. 14 and 15, in the top surface of the bottomwall 3 a of the lower case 3, there is difference in level between afirst wall surface region 42 a which receives the lower edges of theattaching portion 60 a and connecting portion 60 d of the pin retainingmember 60, and a second wall surface region 42 b (shadowed in FIG. 14)which faces the lower edge of the lower arm portion 60 b of the pinretaining member 60. That is, the second wall surface region 42 b isformed into a concave shape with respect to the first wall surfaceregion 42 a.

[0097] Therefore, there is formed a gap between the second wall surfaceregion 42 b and the lower edge of the lower arm portion 60 b. For thisreason, even when the lower arm portion 60 b is deflected, there is nopossibility that it will contact the top surface of the bottom wall 3 aof the lower case 3. Therefore, the operation of the lower arm portion60 b stabilizes and the top surface of the bottom wall of the lower case3 can be prevented from being shaved off by deflection of the lower armportion 60 b.

[0098] Although illustration and explanation are omitted, the portion inthe upper case 2 for attaching the pin retaining member 60 issymmetrical in construction with the portion in the lower case 3 forattaching the pin retaining member 60, as shown in FIG. 16. Therefore,even when the upper arm portion 60 b is deflected, there is nopossibility that it will contact the bottom surface of the top wall 2 aof the upper case 2. As a result, the operation of the upper arm portion60 b stabilizes and the bottom surface of the top wall 2 a of the uppercase 2 can be prevented from being shaved off by deflection of the upperarm portion 60 b.

[0099] In the above-mentioned construction, the installation of the pinretaining member 60 into the cartridge case 4 can be performed byfastening the upper and lower cases 2 and 3 together, and theinstallation is satisfactorily performed. In addition, since the upperand lower flange portions 5 d of the tape leader pin P can be retainedby the single pin retaining member 60, a reduction in the number ofcomponents results in cost reduction. Furthermore, the angled portionsof the upper and lower pin retaining portions 60 c differ in angle sothat when the tape leader pin P is returned into the cartridge case 1,the pin retaining portions 60 c start engaging with the flange portions5 d at difference times. Therefore, smooth engagement of the pinretaining member 60 with the tape leader pin P becomes possible.

[0100]FIG. 18 illustrates a variation of the pin retaining member 60.The upper and lower arm portions 60 b are formed so that they differ inshape. Similarly, the upper and lower pin retaining portions 60 c areformed so that they differ in shape. The upper and lower arm portions 60b may be formed so that they differ in wall thickness.

[0101]FIGS. 19 and 20 illustrate upper and lower torsion coil type pinretaining members 70 formed separately. FIGS. 19A and 20A show an upperpin retaining member 70 _(U) for retaining the upper flange portion 5 dof the tape leader pin P, while FIGS. 19B and 20B show a lower pinretaining member 70 _(D) for retaining the lower flange portion 5 d ofthe tape leader pin P.

[0102] In the pin retaining members 70 _(U) and 70 _(D), a coil portion70 d, an attaching portion 70 a and an arm portion 70 b extending fromthe coil portion 70 d, and a pin retaining portion 70 c formed at theouter end of the arm portion 70 b, are formed by a single line springmember. In FIG. 19, the upper and lower pin retaining members 70 _(U)and 70 _(D) are equipped with the coil portions 70 d differing indiameter from each other. In FIG. 20, the upper and lower pin retainingmembers 70 _(U) and 70 _(D) are equipped with the pin retaining portions70 c differing in shape from each other. That is, the upper and lowerpin retaining members 70 _(U) and 70 _(D) differ in springcharacteristic. Furthermore, the upper and lower pin retaining members70 _(U) and 70 _(D) may be formed into the same shape with differentspring materials. All cases will be satisfied if one of the pinretaining portions 70 c of the upper and lower pin retaining members 70_(U) and 70 _(D) starts engaging with the flange portion 5 d of the tapeleader pin P earlier than the other.

[0103] While the present invention has been described with reference tothe preferred embodiments thereof, the invention is not to be limited tothe details given herein, but may be modified within the scope of theinvention hereinafter claimed.

What is claimed is:
 1. A magnetic tape cartridge comprising: a cartridgecase; a single reel rotatably housed in said cartridge case, said reelhaving magnetic tape wound thereon; and a leader pin, coupled with aleading end of said magnetic tape, for leading said magnetic tape;wherein said leader pin has both a pin main body equipped with a tapeclamp portion on which the leading end of said magnetic tape is wound,and a clamp member for fixing said magnetic tape to said tape clampportion; and a surface of said tape clamp portion is roughened with anaverage surface roughness Rz of 7 μm or less.
 2. A magnetic tapecartridge as set forth in claim 1, wherein a piece of a reinforcementtape is stuck on an outside surface of the leading end of the magnetictape, said outside surface facing to the clamp member.
 3. A magnetictape cartridge comprising: a cartridge case; a single reel rotatablyhoused in said cartridge case, said reel having magnetic tape woundthereon; and a leader pin, coupled with a leading end of said magnetictape, for leading said magnetic tape; wherein said leader pin has both apin main body equipped with a tape clamp portion on which the leadingend of said magnetic tape is wound, and a clamp member, which has anaxial slit and a C cross section, for fixing said magnetic tape to saidtape clamp portion; and an inside surface of said tape clamp member isroughened with an average surface roughness Rz of 7 μm or less.
 4. Amagnetic tape cartridge as set forth in claim 3, wherein a piece of areinforcement tape is stuck on an inside surface of the leading end ofthe magnetic tape, said inside surface facing to the tape clamp portionof the leader pin.
 5. A magnetic tape cartridge as set forth in claim 3,wherein a surface of the tape clamp portion is also roughened with theaverage surface roughness Rz of 7 μm or less.
 6. A magnetic tapecartridge as set forth in claim 5, wherein a piece of a reinforcementtape is stuck on one surface of the leading end of the magnetic tape. 7.A magnetic tape cartridge comprising: a cartridge case in which a singlereel with magnetic tape wound thereon is rotatably housed and a leaderpin coupled with a leading end of said magnetic tape is caught by a pincatching member of a recording-reproducing unit and is inserted into atape leader opening formed in said cartridge case; and a pin retainingspring member which elastically engages said leader pin so that saidleader pin is detachably retained at a predetermined position withinsaid cartridge case; wherein a wall surface is provided in saidcartridge case so that when said leader pin is inserted into saidcartridge case, displacement of said pin retaining member due to theengagement of said pin retaining member with said leader pin isregulated within a predetermined range.
 8. A magnetic tape cartridge asset forth in claim 7, wherein said pin retaining member has an elasticarm portion; and said wall surface faces said elastic arm member with apredetermined space and is approximately perpendicular to a direction inwhich said elastic arm portion is displaced.
 9. A magnetic tapecartridge as set forth in claim 8, wherein said predetermined space isset within an elastic limit of said elastic arm portion.
 10. A magnetictape cartridge as set forth in claim 7, wherein said pin retainingmember has an elastic arm portion; and said wall surface has aconfiguration which corresponds to a pin retaining portion formed in anouter end of said elastic arm portion, and has a protruding portionwhich faces said pin retaining portion with a predetermined space.
 11. Amagnetic tape cartridge comprising: a cartridge case having upper andlower cases fastened together; a single reel, rotatably housed withinsaid cartridge case, which has magnetic tape wound thereon; a leaderpin, coupled with a leading end of said magnetic tape, which has upperand lower flange portions at both ends; upper and lower pin retainingspring members which elastically engage the upper and lower flangeportions of said leader pin so that with an axis of said leader pindirected in a vertical direction, said leader pin is detachably retainedbetween said upper and lower cases; said leader pin being constructed sothat it is caught by a pin catching member of a recording-reproducingunit and moved out of said cartridge case and that it is returned intosaid cartridge case by said pin catching member; wherein said upper andlower pin retaining members have different spring characteristics sothat when said leader pin is returned into said cartridge case, one ofthe pin retaining members starts engaging with the flange portion ofsaid leader pin earlier than the other.
 12. A magnetic tape cartridge asset forth in claim 11, wherein a top surface of a bottom wall of thelower case has a stepped-down portion in a region facing a lower edge ofan active portion of the lower pin retaining member, so as to form a gapbetween the active portion of the lower pin retaining member and the topsurface of the bottom wall of the lower case.
 13. A magnetic tapecartridge as set forth in claim 11, wherein said upper and lower pinretaining members have upper and lower elastic arm portions which differin at least one of wall thickness, shape, or material so that saiddifferent spring characteristics are obtained.
 14. A magnetic tapecartridge as set forth in claim 13, wherein a top surface of a bottomwall of the lower case has a stepped-down portion in a region facing alower edge of the lower elastic arm portion, so as to form a gap betweenthe lower elastic arm portion and the top surface of the bottom wall ofthe lower case.
 15. A magnetic tape cartridge as set forth in claim 11,wherein said upper and lower pin retaining members have upper and lowerelastic arm portions, the arm portions being equipped with upper andlower pin retaining portions bent at difference angles so that saiddifferent spring characteristics are obtained.
 16. A magnetic tapecartridge as set forth in claim 15, wherein a top surface of a bottomwall of the lower case has a stepped-down portion in a region facing alower edge of the lower elastic arm portion, so as to form a gap betweenthe lower elastic arm portion and the top surface of the bottom wall ofthe lower case.